The proposed research would evaluate the utility of high-level radiographic magnification (up to 7X) for the early recognition of tumors. Both regular and tomographic magnification will be applied to in vitro and in vivo animal models that contain either tumors (V2 carcinomas and nitrosourea-induced tumors) or only normal vasculature. Perceptual studies and computer-aided densitometry will be used to determine how effectively magnification improves recognition of small tumors and blood vessels under specified imaging conditions. The resolution and noise properties of the employed film-screen combinations will be parameters. The goal is to develop quantitative relationships between these physical parameters and the perceptual and densiometric findings. The quality of perceptual performance will be determined by analysis of observers' ROC-curves for the in vitro and in vivo detection of tumors and for the detection and delineation of small blood vessels in digitally simulated imagery.